In the exploration for oil and gas, it is necessary to drill a wellbore into the Earth. While drilling of the wellbore permits individuals and companies to evaluate sub-surface materials and to extract desired hydrocarbons, many problems are encountered.
For example, it is well known that the “easy oil” is generally gone. Exploration now requires searching to greater depths than ever before. This necessitates drilling deeper and deeper, and thus into harsh environments, such as those having temperatures ranging from 200 degrees Celsius up to or in excess of 300 degrees Celsius. Generally, present day instrumentation is not built to operate in such an environment, and will fail well before reaching ambient temperatures within this range.
The growing complexity of downhole instrumentation further complicates this problem. That is, as technology continues to improve, exploration is making use of more instrumentation than ever before. With this usage comes an increased demand for power downhole.
Unfortunately, many of the known solutions have substantial drawbacks. For example, various types of batteries suffer catastrophic failure at elevated temperature, and can thus destroy instrumentation. Additionally, such batteries often are not rechargeable, as well as quite expensive.
What are needed are methods and apparatus to provide power downhole in environments that have temperatures ranging from ambient environmental temperatures up to about 200 degrees Celsius or higher, including up to about 300 degrees Celsius.